The invention relates to a charging apparatus for supplying sheet-like, flexible articles, in particular envelopes, these being introduced on edge in stack form, into a station, particularly a station of a mail-processing machine, for further handling, having
an essentially horizontal feed channel for receiving the stacks, which can be moved forward by a first conveying-belt arrangement, which is arranged in the feed channel;
a discharge channel, which leads essentially upward from the end of the feed channel and in which there is provided a second conveying-belt arrangement, which acts on the respectively nearest articles of the stacks; and
a separating or singularizing apparatus, which is likewise arranged in the discharge channel, extends in the direction of the base of the discharge channel and serves for imbricating the stream of articles which is conveyed upward by the stacks.
A problem with such charging apparatuses is that, at the transition from the feed channel to the discharge channel, the sheet-like articles butt against one another in a very closely packed manner and are pressed against one another if the conveying-belt arrangement of the feed channel conveys articles up at a greater speed than the speed with which they are discharged by the conveying-belt arrangement in the discharge channel. This may result in irregular functioning of the separating device, such that the imbricated stream of discharged articles has irregularities and the separating result is not satisfactory. If the charging apparatus is a station of a mail-processing machine which is arranged upstream of an envelope-filling station, then the result may be, in the previously briefly described state of excessively close packing of envelopes in the transition region between the feed channel and the discharge channel, that the stream of envelopes conveyed upward in the discharge channel is subjected to irregular imbrication by the separating device to such an extent that individual envelopes are no longer conveyed up in the envelope-filling station, and this results in disruption to operation.
In order to avoid this disadvantage, an attempt has also already been made, in the feed channel, for the stacks of sheet-like articles which are to be conveyed forward to be moved by gravitational force rather than by a conveying-belt arrangement, for which purpose the feed channel has been oriented obliquely downward, with the result that the stacks of sheet-like articles, standing on edge, slid downward in the direction of the conveying-belt arrangement of the discharge channel. Such a charging apparatus is described in International Patent Application WO 99/08951.
In a fair number of cases, however, it may be expedient for the operation of moving a long stack or stacks of flat articles, which are introduced on edge, in the feed channel of a charging apparatus of the type under discussion here not to be rendered dependent on a certain gradient of the feed channel or on certain sliding properties of the articles, which are introduced on edge.
The object of the present invention is thus to configure a charging apparatus of the type defined in the introduction such that a uniform separating result is reliably achieved for the imbrication of the stream of upwardly-conveyed articles.
This object is achieved according to the invention in that, in the case of a charging apparatus having the features as have been defined in the introduction, provided at the transition of the feed channel to the discharge channel is a rib or sill which runs transversely to the conveying direction and, in relation to a vertical section in the conveying direction, takes such a cross-sectional course that articles which have crossed the rib or sill in the conveying direction by way of their bottom edge come into a position in which they are parallel, for example, to the conveying direction of the further conveying-belt arrangement, and are gripped one by one by the further conveying-belt arrangement such that in the region of the rib or sill, when the first conveying-belt arrangement is at a standstill or is running more slowly, a gap which is parallel to said rib or sill opens between the bottom edges of articles which are located in front of the rib or sill and the bottom edges of articles which have already passed the rib or sill, and in that installed at the transition of the feed channel into the discharge channel are a light transmitter and a light sensor for forming a light barrier which produces a detector signal which indicates the formation of said gap and can be supplied to a control apparatus for controlling a drive of the first conveying-belt arrangement.
If the charging apparatus is brought into operation, then one or more stacks of sheet-like articles which are to be introduced are positioned in the feed channel and the bottom edges of the sheet-like articles are supported on the first conveying-belt arrangement, which is located in the feed channel. The sheet-like articles also fill the feed channel in a closely packed manner in the region of the transition between the feed channel and the discharge channel. The light barrier, of which the detector light beam crosses over the channel width from one side of the transition region between the feed channel and discharge channel, remains obstructed by the stack of sheet-like articles which are to be conveyed, and the first conveying-belt arrangement, which is located in the feed channel, is brought to a standstill.
If the second conveying-belt arrangement, in the discharge channel, is then brought into operation, since sheet-like articles are required in the further handling station, for example in the envelope-filling station, then the second conveying-belt arrangement, which is located in the discharge channel, draws sheet-like articles upward past the separating device, and that part of the stack which is located in the transition region between the feed channel and the discharge channel is reduced in thickness. This then produces, in said transition region, a wedge-shaped gap through which the detector beam emitted by the light source can pass from one side of the channel to the other and come into contact with the light detector. This produces a light-barrier detector signal which brings the conveying-belt arrangement of the feed channel into operation and resumes the interspace-free or gap-free packing of the stack of sheet-like articles in the apparatus.
Advantageously, the light barrier does not respond to brief interruptions, and a certain time delay is provided between the interruption of the light barrier and the drive of the first conveying-belt arrangement of the feed channel being brought out of operation, it being possible for this time delay to be adjusted.
According to an advantageous modification, it is also possible for the detector signal of the light barrier to be used, in accordance with specific processing, to coordinate the respective conveying speeds of the conveying-belt arrangements in the feed channel and in the discharge channel with one another, with the result that more or less continuous operation is achieved.